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IP Secondary 4 Biology > Chapter 2 - Homeostasis > Flashcards

Chapter 2 - Homeostasis Flashcards

1
Q

What does homeostasis do?

A

Ensures that the internal conditions of an organism are kept constant all the time

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2
Q

What is the importance of homeostasis?

A

A stable internal environment allows an organism to be independent of changes in the external environment

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3
Q

What are the internal conditions that should be kept constant?

A 
Temperature
pH
Water potential 
Concentration of metabolic wastes  
Blood glucose concentration 
Carbon dioxide concentration
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4
Q

Why must temperature and pH level be kept constant?

A

Enzymes require an optimum temperature and pH to function properly

  • Below the optimum temperature, enzymes are inactivated. Beyond the optimum temperature, enzymes are denatured
  • Drastic changes in pH level in the blood affect the activity of enzymes and the rate of cellular reactions
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5
Q

How must water potential be kept constant?

A

The composition of tissue fluid has to be maintained

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6
Q

Why must water potential be kept constant?

A

Changes in the water potential affect the body cells

- Body cells will either shrink or burst in solutions with water potentials different from that in the cytoplasm

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7
Q

Why must blood glucose level be kept constant?

A

Glucose in food is required for tissue respiration which releases energy for cells to carry out their activities

  • Glucose levels increase after a meal and decrease following physical exertion
  • If blood glucose concentration changes drastically, it can be dangerous
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8
Q

What are the principles of homeostasis?

A
  • A stimulus is a change from normal conditions in the internal environment
  • Receptors detect stimulus
  • A corrective mechanism brings about the reverse effect of the stimulus
  • Negative feedback ‘tells’ the receptors that the condition has been restored back to normal state
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9
Q

What happens when a condition rises above normal?

A

Normal condition or set point → Stimulus (increases above norm) → Receptor (detects the stimulus) → Self-regulatory corrective mechanism → Condition decreases (+negative feedback to receptor) → Normal condition or set point

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10
Q

What happens when a condition decreases below normal?

A

Normal condition or set point → Stimulus (decreases above norm) → Receptor (detects the stimulus) → Self-regulatory corrective mechanism → Condition increases (+negative feedback to receptor) → Normal condition or set point

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11
Q

Regulating blood glucose concentration: excess glucose

A
  1. Stimulus: Concentration of blood glucose increases above the norm
  2. Receptor: Islets of Langerhans in pancreas stimulated
  3. Corrective Mechanism: Islets of Langerhans secretes more insulin, which is transported by blood to liver and muscles
  4. Permeability of cell surface membrane to glucose increases
  5. Liver and muscles convert excess glucose to glycogen. Glycogen is stored in liver and muscles.
  6. Concentration of blood glucose decreases and insulin production falls
  7. Concentration of blood glucose returns to normal
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12
Q

Regulating blood glucose concentration: insufficient glucose

A
  1. Stimulus: Concentration of blood glucose decreases above the norm
  2. Receptor: Islets of Langerhans in pancreas stimulated
  3. Corrective Mechanism: Islets of Langerhans secretes more glucagon, which is transported by blood to liver and muscles
  4. Glycogen stored in liver is converted to glucose
  5. Glucose is released into the bloodstream
  6. Concentration of blood glucose increases and glucagon production falls
  7. Concentration of blood glucose returns to normal
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13
Q

Regulating body water potential: too high

A
  1. Stimulus: Water potential of blood increases above the norm
  2. Receptor: Hypothalamus in brain detects stimulus
  3. Corrective Mechanism: Pituitary gland releases less ADH
  4. Less water is reabsorbed by kidney tubules
  5. More water is excreted and urine produced is more dilute
  6. Water potential of blood decreases
  7. Water potential of blood returns to normal
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14
Q

Regulating body water potential: too low

A
  1. Stimulus: Water potential of blood decreases below the norm
  2. Receptor: Hypothalamus in brain detects stimulus
  3. Corrective Mechanism: Pituitary gland releases more ADH
  4. More water is reabsorbed by kidney tubules
  5. Less water is excreted and urine produced is more concentrated
  6. Water potential of blood increases
  7. Water potential of blood returns to normal
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15
Q

Epidermis: Describe the cornified layer

A
  • The outermost surface of the skin
  • Consists of dead dry cells with keratin deposits
  • Dead cells are continuously shed from skin surface
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16
Q

Epidermis: Describe the granular layer

A
  • The middle layer of the epidermis
  • Consists of living cells that move upwards
  • Cells eventually become dry and dead to form cornified layer
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17
Q

Epidermis: Describe the Malpighian layer

A
  • The innermost layer of the epidermis

- Consists of actively dividing cells that contain melanin

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18
Q

Describe the dermis

A
  • Found directly below the Malpighian layer
  • Upper part is thrown into ridges or papillae
  • Has numerous blood capillaries supplying blood to skin
  • Hairs are embedded within the dermis
19
Q

What is vasodilation?

A

When blood vessels dilate and as a result more blood flows to the skin surface

20
Q

What is vasoconstriction?

A

When blood vessels constrict and as a result less blood flows to the skin surface

21
Q

Vasodilation and vasoconstriction play a role in the ________

A

regulation of body temperature

22
Q

Skin hair: Describe hair follicle

A

Malpighian layer sinks into dermis to form a hair follicle

23
Q

Skin hair: Describe hair papilla

A
  • Found at the base of the hair follicle

- Consists of blood capillaries and nerves

24
Q

Skin hair: Describe hair erector muscles

A

Contract and cause hairs to stand, resulting in the appearance of goose pimples

25
Q

Describe sebaceous glands

A
  • Open into each hair follicle

- Secrete sebum which lubricates the hair, keeps the skin soft and prevents microbial growth

26
Q

Describe sweat gland

A
  • A coiled tube formed by the downgrowth of the epidermis
  • Richly surrounded by blood capillaries
  • Secretes sweat which flows through the sweat duct and sweat pore to the skin surface
27
Q

Describe sub-cutaneous fat

A
  • Found beneath the dermis

- Consists of adipose cells which store fats

28
Q

What are some instances of heat gain by the body?

A
  • From the Sun and warm air on hot days
  • Intake of hot food and drinks
  • Metabolic activities taking place in the body release heat
  • During physical exertion or exercise
29
Q

What are some instances of heat loss by the body?

A
  • From the skin surface via convection, radiation and conduction
  • Evaporation of sweat
  • Expired air from lungs
  • Faeces and urine
30
Q

What does thermoregulation do?

A

Thermoregulation helps to maintain the human body temperature at about 37°C

31
Q

Regulating body temperature: hot day

A
  1. Stimulus: Blood and skin temperatures increase
  2. Receptor: Temperature receptors in skin and hypothalamus of brain stimulated
  3. Corrective Mechanism
  4. Increased heat loss and reduced heat production
  5. Body temperature decreases
  6. Blood and skin temperatures return to normal
32
Q

Regulating body temperature: what is the corrective mechanism (hot day)?

A
  • Vasodilation of arterioles near skin’s surface
  • Increased production of sweat
  • Increased rate of breathing
  • Metabolic rate decreases
33
Q

Regulating body temperature: how does vasodilation lead to heat loss (hot day)?

A
  1. Arterioles in skin dilate
  2. More blood flows to capillaries in skin
  3. Shunt vessel constricts
  4. More heat is lost from skin by radiation, convection and conduction
34
Q

Regulating body temperature: how does increased production of sweat lead to heat loss (hot day)?

A
  1. Sweat glands become more active
  2. More sweat is produced
  3. More latent heat is removed when sweat evaporates
35
Q

Regulating body temperature: how does relaxation of hair erector muscles lead to heat loss (hot day)?

A

Hairs lie flat, allowing air to circulate over skin. This

removes heat.

36
Q

Regulating body temperature: how does reduced metabolic rate lead to heat loss (hot day)?

A

Less heat is produced within body

37
Q

Regulating body temperature: cold day

A
  1. Stimulus: Blood and skin temperatures decrease
  2. Receptor: Temperature receptors in skin and hypothalamus of brain stimulated
  3. Corrective Mechanism
  4. Decreased heat loss and increased heat production
  5. Body temperature increases
  6. Blood and skin temperatures return to normal
38
Q

Regulating body temperature: what is the corrective mechanism (cold day)?

A
  • Vasoconstriction of arterioles near skin’s surface
  • Decreased production of sweat
  • Metabolic rate increases
  • Shivering
39
Q

Regulating body temperature: how does vasoconstriction lead to reduced heat loss (cold day)?

A
  1. Arterioles in skin constrict
  2. Less blood flows to capillaries in skin
  3. Shunt vessel dilates
  4. Less heat is lost from skin by radiation, convection and conduction
40
Q

Regulating body temperature: how does decreased production of sweat lead to reduced heat loss (cold day)?

A
  1. Sweat glands become less active
  2. Less sweat is produced
  3. Less latent heat is removed when sweat evaporates
41
Q

Regulating body temperature: how does contraction of hair erector muscles lead to reduced heat loss (cold day)?

A

Hairs “stand up”, trapping an insulating layer of warm air over skin

42
Q

Regulating body temperature: how does increased metabolic rate lead to reduced heat loss (cold day)?

A

More heat is produced within body

43
Q

Regulating body temperature: how does shivering lead to reduced heat loss (cold day)?

A

Reflex contraction of the body muscles generates heat which increases body temperature to normal

44
Q

Regulating body temperature: when does shivering occur?

A

When more heat production is needed to prevent drop in temperature

IP Secondary 4 Biology (6 decks)

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